1. Field of the Invention
The present invention relates to a cooling device for cooling a battery for running mounted on a vehicle such as a hybrid car, and a power supply including the same.
2. Description of Related Art
In recent years, hybrid electric vehicles (in the following, referred to as hybrid cars) on which an engine and a motor are mounted as a driving source have been commercialized and attracted attention. A hybrid car includes a secondary battery (a power supply) as a power source for supplying an electric power to a driving motor. In this secondary battery, charging or discharging is conducted according to the state of running of the vehicle.
Further, the secondary battery to be mounted on the hybrid car generates a large amount of heat because it is a combination of many single cells. Also, an electrochemical reaction at the time of charging or discharging in the secondary battery depends on a temperature. Thus, when the temperature of the secondary battery exceeds a particular temperature, there arise problems of deteriorating performance of the secondary battery and a shortened lifetime thereof. Accordingly, as shown in JP 2002-120568 A, JP 2001-354039 A and JP 2004-136767 A, the power supply in the hybrid car conventionally has included a cooling device for cooling the battery.
FIG. 10 is a sectional view showing a configuration of a conventional power supply. The power supply shown in FIG. 10 includes a battery pack 110 and a cooling device. The cooling device supplies an air to an inner part of the battery pack 110 and cools the battery pack 110 with the supplied air.
More specifically, the battery pack 110 has a configuration in which a plurality of unit cells 111 are disposed in a battery case 112. The battery case 112 is provided with a supply port 113 for supplying the air to its inner part and an exhaust port 114 for discharging the air after heat exchange. Furthermore, gaps are provided between the adjacent unit cells 111 and between each unit cell 111 and an inner surface of the battery case 112 and serve as a passage for the supplied air.
The cooling device includes an intake duct 101, an exhaust duct 102 and a fan unit 103. The intake duct 101 connects the supply port 113 of the battery case 112 and an air inlet 109 provided in an interior material 108 of the vehicle. Also, at an opening of the intake duct 101 on the side of the air inlet 109, a filter member 107 is disposed for preventing the entry of foreign objects into the battery pack 110.
The exhaust duct 102 connects the exhaust port 114 of the battery case 112 and a suction port 103a of the fan unit 103. The fan unit 103 includes a housing 106, a fan 104 disposed in the housing 106 and a motor 105 for driving the fan 104. The housing 106 is provided with the suction port 103a and an exhaust port 103b. 
When the fan 104 is driven by the motor 105, the air in a vehicle interior is supplied through the intake duct 101 to the inner part of the battery case 112, so that the temperature rise in each of the unit cells 111 is suppressed. Further, the air that has been warmed up by the unit cells 111 passes through the exhaust duct 102 and is released from the exhaust port 103b provided in the housing 106 of the fan unit 103 to the outside of the vehicle.
Moreover, the cooling device shown in FIG. 10 includes a control device 120. The control device 120 includes a judging portion 121, a motor driving portion 122 and a temperature detecting portion 123 and switches a fan speed of the fan 104 between multiple stages (for example, “LOW”, “MIDDLE” and “HIGH”) according to the temperature of the unit cell 111. The motor 105 is driven by a constant voltage system.
More specifically, the temperature detecting portion 123 detects the temperature of the unit cell 111 based on a signal from a temperature sensor 124 attached to the unit cell 111. The judging portion 121 judges whether the present fan speed is suitable for the detected temperature.
If not, the judging portion 121 selects a fan speed suitable for the detected temperature. In this case, the judging portion 121 further outputs a signal (a fan speed indicating signal) to the motor driving portion 122 so that a voltage corresponding to the selected fan speed is applied to the motor 105.
The motor driving portion 122 switches the voltage applied to the motor 105 between multiple stages according to the indication of the judging portion 121 so as to adjust the fan speed of the fan 104 in stages. Thus, in the case where the judging portion 121 outputs the fan speed indicating signal, the motor driving portion 122 switches the voltage so that the fan 104 rotates at the selected fan speed.
In this manner, the control device 120 operates the fan 104 while switching the fan speed between multiple stages so that the temperature of the unit cell 111 does not exceed a preset threshold, and suppresses the temperature rise of the unit cell 111.
In the above-described conventional power supply illustrated in FIG. 10, the filter member 107 becomes clogged with the passage of operation time of the fan 104. Accordingly, the volume of the air supplied to the inner part of the battery case 112 (in the following, referred to as a “supply air volume”) also decreases gradually with the passage of operation time of the fan 104. If such a situation is left unaddressed, it becomes impossible to suppress the temperature rise of the unit cell 111 even by operating the fan 104. This deteriorates the performance of the unit cell 111 and shortens the lifetime thereof.
Furthermore, there also are some cases where the supply air volume decreases due to a cause other than the clogging of the filter member 107, for example, where a foreign object blocks the air inlet 109 or a foreign object staves in the filter member 107 and intrudes into the intake duct 101. In these cases, the temperature rise cannot be suppressed, which deteriorates the performance of the unit cell 111 and shortens the lifetime thereof, similarly to the case where the filter member 107 is clogged. Consequently, in the above-described conventional power supply illustrated in FIG. 10, it is necessary to monitor the clogging of the filter member 107 and the decrease in the supply air volume due to foreign objects.
Also, in the field of air conditioning equipment such as a warm-air heater, an air conditioner that senses the filter clogging automatically has been known. For example, JP 2002-147863 A discloses a method for sensing a filter clogging in a warm-air heater based on the amount of changes in a control value of a fan motor when the filter is not clogged (a reference control value) and a control value of the fan motor outputted for maintaining the number of revolutions of the fan to a target number of revolutions.
However, in the above-described conventional power supply illustrated in FIG. 10, the control device 120 has only the function of detecting the temperature of the unit cell 111 and no function of sensing a decrease in the supply air volume due to clogging or the like of the filter member 107. Therefore, it is not until the temperature of the unit cell 111 rises that a user realizes the clogging of the filter member 107 or the presence of a foreign object in the intake duct 101. Also, after the temperature of the unit cell 111 rises, the performance deterioration of the unit cell 111 and the shortening of the lifetime thereof already might be caused.
On the other hand, if a user periodically cleans or replaces the filter member 107 or carries out an inspection in the air inlet 109 and the intake duct 101, the above-mentioned problems can be avoided. However, it is up to a user to do such a work, and a user conceivably might fail to do such a work.
Further, applying the method disclosed in JP 2002-147863 A to the above-described conventional power supply illustrated in FIG. 10 also can be considered. However, in this case, the number of revolutions of the fan has to be sensed, leading to an increase in the cost of the power supply. Moreover, in order to obtain the control value of the motor 105, it is necessary to control the motor 105 by the control method disclosed in JP 2002-147863 A, which also increases the cost of the power supply.
It is an object of the present invention to solve the problems described above and to provide a cooling device capable of sensing an anomaly in a supply air volume due to clogging of a filter provided in an air supply channel in a battery mounted on a vehicle or a foreign object, and a power supply including the same.